Source for water flow switches suitable for lasers?

Methods of cooling laser tubes

Re: Source for water flow switches suitable for lasers?

Postby hoda0013 » Tue Nov 16, 2010 2:40 pm

I have two of these flow switches from McMaster:

42015K21

I believe they are the Gems brand. I haven't used it with flowing water yet, but they do work when I simply blow through them. I think that I'm going to hook up the leads from the WP pin on my power supply to ground. This should disable the supply if the water is not flowing. Does anyone else have a different lockout scheme than that?
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Re: Source for water flow switches suitable for lasers?

Postby bdring » Tue Nov 16, 2010 2:47 pm

That switch is for 0.5 liter/min. Isn't that a little low?
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Re: Source for water flow switches suitable for lasers?

Postby Mark K » Tue Nov 16, 2010 3:02 pm

Seeed studio has two devices, one a switch and one a flow meter.

http://www.seeedstudio.com/depot/sensor ... f601e4850c

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Re: Source for water flow switches suitable for lasers?

Postby hoda0013 » Tue Nov 16, 2010 3:25 pm

@bdring:

I can't be sure that it will work, but two of them were included in an ebay auction that I won, so I'm going to try one out. I think the .25 gal/min. is the minimum flow that will trip the switch, but I think I can still pump fluid through the switch at a higher rate (I hope). My cooling system will be closed loop with a large radiator and two fans as well. If the water flow is restricted to a low rate, I hope the fans will be able to pull the heat out. I'll post what I find when I do the test.
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Re: Source for water flow switches suitable for lasers?

Postby twehr » Fri May 27, 2011 6:55 pm

Has anybody seen/heard/tried this:

http://www.futurlec.com/Flow_Sensor.shtml (next to last item on page)

FLOWMETER2.jpg


If it works, it is a good price ($18.90) for a sensor with a build-in flow rate readout. No switching for auto shutdown, but at least we could see the flow rate.

(I have ordered from this company before - think they are in China and it takes a couple of weeks to get product here, but they seemed reliable and honest when I ordered from the in the past.)
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Re: Source for water flow switches suitable for lasers?

Postby bdring » Sat May 28, 2011 12:39 am

I have ordered for years from Futurlec. They have great prices, but it takes about 2 weeks to get your stuff.

The meter is cool, but like you said, it will not shut down the laser. Those switches can be had in the $5-$6 range. They are not much different than the paddle wheel some of us sort of use now. The switch needs an active circuit to monitor the pulses. It could be as simple as a 555 missing pulse detector or a microcontroller. I did it once before using a PSOC controller. I would probably use a PIC16F88 now. A 16F88 has zero external components and is dirt cheap.

psoceval1.JPG


http://www.buildlog.net/cnc_laser/mach_ ... intfc.html
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Re: Source for water flow switches suitable for lasers?

Postby rogue555 » Sat May 28, 2011 1:16 pm

A laser we had at my old lab used a pressure switch to sense flow. It was set up to switch on vacuum and tapped into the coolant flow line. This way it sensed the drop in pressure due to flow and would switch on. I'm not sure which manufacturer made the switch but I've seen similar stuff from Omega (but at around $25 a piece).

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Re: Source for water flow switches suitable for lasers?

Postby bdring » Sat May 28, 2011 1:44 pm

A true flow switch is best. A pinched line can fool a pressure switch. Placement of the switch can help. If you put it after any place that might pinch you are OK, but if you are too far down the line there may not be a lot of pressure to measure. Some flow switches have a low side and high side, so you measure the pressure across your laser. A blocked line would not show any pressure across the laser. This can get a little complicated to hook up though.

A flow switch right after the laser is best. Many of the Chinese lasers use a cheap flow sensor. It is basically a magnet in a plastic cylinder. The flow causes the magnet to move to a reed switch. I can get these in quantity for about $10, but I would need to order a bunch of them and they are not adjustable, so you need to know the exact flow. Some have springs and some relay on gravity to return the magnet when flow drops.

flowswitch.JPG
flowswitch.JPG (16.37 KiB) Viewed 3147 times
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Re: Source for water flow switches suitable for lasers?

Postby BenJackson » Sat May 28, 2011 6:36 pm

bdring wrote:I can get these in quantity for about $10, but I would need to order a bunch of them and they are not adjustable, so you need to know the exact flow.

You just need to choose a minimum flow suitable for the laser (eg the 250gph that FSE mentions). People can still buy bigger pumps.

I'm still interested in sources since I haven't even found a reasonably priced place to get the Koolance one.
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Re: Source for water flow switches suitable for lasers?

Postby aXit » Sun Jun 12, 2011 10:24 am

Lightobject actually has some availaible

http://www.lightobject.com/Search.aspx?k=flow

3 sizes, looks to be the standard screw fittings.
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